Regular sequential copolyesters



United States Patent "ice 3,440,221

Patented Apr. 22, 1969 isophthalic acid, 1,2,3,4,5,6,7,8-octahydroanthracence di- 3,440,221 carboxylic acid-9,10, and 1,3,5,7-tetramethylnaphthalene REGULAR SEQUENTIAL COPOLYESTERS Richard Keith Quisenberry, Kinston, N.C., assignor to E. I. du Pont de Nemours and Company, Wilmington,

dicarboxylic acid-2,6. These are aromatic dicarboxylic acids having the carboxyl groups in non-adjacent positions Del" a corporation of Delaware 5 on an aromatic nucleus with alkylor chloro-substituents No Drawing. Filed Mar. 4, 1966, Ser. No. 531,731 ortho to the carboxyl q p I t, (1 C08g 17/08 In a preferred embodiment of the invention the copoly- U.S. Cl. 260-75 4 Claims ester is prepared from terephthalic acid, ethylene glycol,

and a sterically hindered dicarboxylic acid, and may be 10 represented as comprising regularly recurring units of ABSTRACT or THE DISCLOSURE the formula A fiber-forming linear copolyester having a regular se- H H H quential molecular structure of recurring units represented O(CH2)2OCRCO(C H2)2OCC by the formula wherein R is a divalent radical from the group consisting l u i n -o oHi)Z-o-o-a-o-o-wmn-o-o-Q-oon,

CH3 CH3 wherein R is a radical of a sterically hindered aromatic Q- a dicarboxylic having the carboxyl groups in non-adjacent positions on the aromatic nucleus. CH3 CH3 The radicals R are derived from 2,3,5,6 tetramethyl- This invention relates to linear polyesters and, more terephthalic acid and 2,4,6-trimethylisophthalic acid.

particularly, to fiber-forming linear copolyesters having Usually it is preferred that the linear copolyester have a regular sequential molecular structure. an intrinsic viscosity of at least 0.35, as measured in solu- Methods of preparation and useful properties of polytion at 25 C. in a mixture of 3 parts trifiuoroacetic acid esters prepared from glycols and dicarboxylic acids are and 1 part methylene chloride by weight.

well known. For example, fibers and films prepared from The copolyesters of the invention may be prepared by polyethylene terephthalate, as described in Whinfield et al. first forming the bis-glycol ester of the sterically hindered US. Patent No. 2,465,319, dated Mar. 22, 1949, have bedicarboxylic acid and then carrying out, at an elevated come standard articles of commerce. It is also known that temperature, an ester-interchange condensation reaction major changes in polymer properties may be obtained by between this bis-glycol ester and a lower-alkyl di-ester of preparing the polyester from a mixture of two different terephthalic acid. Surprisingly, the ester linkage adjacent acids or from a mixture of two dififerent glycols. Howto the sterically hindered acid residue in the bis-glycol ever, when copolyesters of this type are prepared by ester is sufliciently stable to remain inert in a reaction of usual methods, random copolymers result which have this type. Consequently, the copolymer produced contains sharply reduced melting points and are diflicult to crysthe two acid groups in a 1:1 ratio and in regular altertallize. nating sequence. This reaction may be illustrated as fol- The present invention provides a novel class of copolylows for the preparation of poly(ethylene 2,3,5,6-tetraesters prepared from a glycol and two different dicarmethylterephthalate/ethylene terephthalate):

CH3 CH3 0 0 o o nHOCHzCHgO 3O-CH2CHzOH nCH3O iOOH,-, r

(EH3 CH:

boxylic acids wherein the molecular structure consists of 5,5 wherein n is a large integer. regular sequential units of the following type: The above reaction is usually carried out in the presence of a catalyst. Suitable catalysts include tetrabutyl [glycol acldl glycol acldz] titanate, manganous acetate and antimony oxide, calcium These polymers are considerably easier to crystallize and acetate, and lead oxide. have a much higher melting point than the corresponding The bis-glycol ester of the sterically hindered acid used random copolymers. in the above reaction may be prepared by reacting the so- The novel copolyesters of the invention are derived dium salt of the acid with 2-chloroethanol. Alternatively from a glycol of the class HO(CH OH, Where x is the bis-glycol ester may be prepared by reacting the di- 2-10, and two different carboxylic acids, with one of the acid chloride of the sterically hindered acid with an exacids being characterized by a high degree of steric hincess of ethylene glycol.

drance in that part of the molecule adjacent to the car- The novel copolyesters of this invention are well suited boxylic group. Preferably, the sterically hindered acid is to a variety of applications. Then can be readily melt an aromatic dicarboxylic acid having bulky substituents spun into filaments or cast from solutions to form selfon ring carbon atoms ortho to the carboxylic groups. Exsupporting films. Their properties make them particularly amples of suitable sterically hindered acids include 2,3,5,6- 7O advantageous for use in synthetic fibers for conversion tetramethylterephthalic acid, 2,4,6 trimethylisophthalic to textiles, films, tapes and other shaped articles obtained acid, 2,3,5,6-tetrachloroterephthalic acid, 2,4,6-trichloroby using the polyesters as molding compositions.

The expression polymer melt temperature employed with respect to the products of this invention is the min imum temperature at which a sample of the polymer leaves a wet molten trail as it is stroked with moderate pressure across a smooth surface of a heated metal bar. Polmer melt temperature" has sometimes in the past been referred to as polymer stick temperature.

The term intrinsic viscosity, as used herein, is defined as the limit of the fraction ln(r)/c as c approaches 0, where (r) is the relative viscosity, and c is the concentration in grams per 100 ml. of solution. The relative viscosity (r) is the ratio of the viscosity of a solution of the polymer, in a mixture of 3 parts trifluoroacetic acid and one part methylene chloride by weight, to the viscosity of the trifiuoroacetic acid/methylene chloride mixture, per se, measured in the same units at C. Intrinsic viscosity is a measure of the degree of polymerization.

This invention is further illustrated, but is not intended to be limited, by the following examples in which parts and percentages are by weight, unless otherwise specified.

EXAMPLE I A standard polymer tube is charged with bis[2-hydroxyethyl] 2,3,5,6 tetramethylterephthalate (25.0 g., 0.081 mol), dimethylterephthalate (6.8 g., 0.035 mol), and tetrabutyl titanate (0.080 g. in 1.6 ml. n-butanol). The tube is heated at 170220 C. for three hours during which time 3.2 ml. of methanol is removed by distillation. The temperature of the tube is then raised to 275- 280 C. for 4.75 hours, with the pressure being reduced to 0.3 mm. Hg. During this period excess bis[2-hydroxyethyl] 2,3,5,6 tetramethylterephthalate is removed through the vacuum system. Upon cooling the tube, a crystalline polymer is formed which is found to have a PMT of 269 C. and an intrinsic viscosity of 0.69. The polymer exhibits a distinctive X-ray diifraction pattern confirming its crystallinity. The polymer is insoluble in chlorinated hydrocarbons and ketones.

Degradation of the polymer and analysis of the products by gas chromatography confirms that the two acids are present in a 1:1 mol ratio.

The copolyester is melt spun at 300 C. and the fiber produced is drawn 3.5x at 150 C. After a mock finishing treatment the fiber is tested for recovery properties and found to give a TSR value of 65. Dyeability tests with dispersed dyes indicates that the dyeability of the fiber is substantially equivalent to that of a fiber spun from polyethylene terephthalate in similar fashion.

The mock finishing procedure used above comprises the consecutive steps of: (a) heat-treating the filaments by boiling them in water for 15 minutes while allowing 3% shrinkage in length, (b) heating the filaments in an oven at 180 C. for three minutes, again allowing 3% shrinkage in length, (c) heat-treating the filaments by boiling them in water for 15 minutes while allowing 1% shrinkage in length, and finally ((1) air drying the filaments.

The TSR of a yarn sample is determined by mounting a. 10-inch length of the yarn on a tensile tester (commercially available from the Instron Engineering Corporation, Quincy, Mass). The sample is then immersed in a water bath maintained at 40 C. for a period of 2 minutes and then stretched, in the water bath, at an elongation rate of 1 inch (2.54 cm.) per minute. Upon reaching the desired total elongation, the sample is held at constant length for an additional 2 minutes and the water bath is removed. The load on the yarn is then reduced to a value of 0.042 g.p.d. and the yarn is allowed to retract. Percent recovery is calculated from the formula:

units of retraction units of elongation 100 cent recovery against total elongation in the range 03%. TSR values are average percent recovery values from the range 03% elongation which may be determined from the graph by usual graphical averaging procedures. Yarns having TSR values of 60% are considered to have good tensile recovery.

For comparison it is interesting to note that a random copolymer having an intrinsic viscosity of 0.65 prepared by another route, in which the ratio of tetramethylterephthalate units to terephthalate units is 48:52, has a PMT of only 160 C. and cannot be made to crystallize.

EXAMPLE II The polymer preparation procedure of Example I is repeated using bis[2 hydroxyethyl] 2,4,6-trirnethylis0- phthalate in place of bis[2-hydroxyethyl]-2,3,5,6-tetramethylterephthalate. A high-melting crystalline solid is produced which is capable of being melt spun into fibers. By degradation of the polymer and analysis of the products it is confirmed that the ratio of 2,4,6-trimethylisophthalate units to terephthalate units is 1:1.

The following method may be employed to produce bis[2hydroxyethyl] 2,3,5,6 tetramethylterephthalate from the free acid. The preparation of the acid itself is described in Koenecke et al. US. Patent No. 2,806,877 dated Sept. 17, 1957.

Into a 1 liter flask equipped with a heating mantle, stirrer, and reflux condenser is placed 400 ml. water and 14.4 grams (0.36 mol) sodium hydroxide. To this is added 40.0 grams (0.18 mol) 2,3,5,6 tetramethylterephthalic acid. After the acid is dissolved, 50 grams (0.6 mol) 2-chloroethanol and 0.25 gram sodium iodide are added. The solution is stirred at reflux temperature for 24 hours, and then cooled to give 53 grams of a white solid. After recrystallization from ethylene chloride, the solid is found to melt at -141" C. Analysis calculated for C H O C, 61.9; H, 7.15. Found: C, 61.7; H, 7.12.

Bis[Z-hydroxyethyl]-2,4,G-trimethylisophthalate is prepared from 2,4,6-trimethylisophthalic acid in a similar fashion. The preparation of the acid itself is disclosed in Beilstein, Handbuch Der Organischen Chemie, vol. IX (1926), p. 884(19).

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. A polymeric fiber-forming linear copolyester having a regular sequential molecular structure consisting essentially of recurring units represented by the formula,

0 II II wherein R is a divalent radical from the group consisting of CH CH3 CH and CH: OH:

H; CH3

3,440,221 5 6 ing the trimethyli'sophthalate and the terephthalate groups FOREIGN PATENTS arranged in regular alternating sequence. 1,342,483 9/ 1963 France References Cited UNITED STATES PATENTS 5 LOUISE P. QUAST, Assistant Examiner.

3,341,500 9/1967 Schwarz 260-75 3,013,914 12/1961 Willard 260-75 3,037,964 6/1962 Bruson a a1. s 2 -4 0; 2 4 12 WILLIAM H. SHORT, Primary Examiner. 

